About Bihar Diwas :: Bihar Diwas ( बिहार दिवस ) or Bihar Day is observed every year on March 22, marking the formation of the state of Bihar. It was on this day when the British carved out the state from Bengal Presidency in 1912. The Day is a public Holiday in Bihar. Bihar Divas was started and celebrated on large scale by Bihar Government in the tenure of Nitish Kumar. Apart from India, it is celebrated in countries including United States, Britain, Australia, Canada, Bahrain, Qatar, United Arab Emirates, Trinidad and Tobago and Mauritius.